Shelter island, shelter island heights. Worcester again have the best efficiencies of the group, achieving an incredible 94% on both models! their 10 year guarantee on the 30si model is matched only by vaillant (when fitted by an accredited installer), however it is again the most expensive the baxi eco blue has the best output of the group both in heating and hot water flow rates and at a great price. Cfm ventilation project. Both your engineers.